Easy as going to Home Depot and buying a couple caps. Provided you have a standard size drain/return (most RR tanks do).
I'm going the exact same thing, well... not waiting until summer, but a couple weeks. I had the same question yesterday when I ordered my Oceanic RR.
Marine Tank: Oceanic 58 Gallon RR â–* Established October 2004
Planted Tank: Oceanic 58 Gallon â–* Established September 2005